There is known a technology of measuring a circuit pattern state in the middle of a manufacturing process of semiconductor devices. This technology is positioned to be critical to the manufacturing yield improvement and the quality management. The critical dimension measurement SEM (Scanning Electron Microscopy) for measuring circuit pattern dimensions is one of technologies for measuring circuit pattern states. The critical dimension measurement SEM uses a high resolution and a long focal depth specific to SEM to measure dimensions in a transverse direction (in-plane direction) of a circuit pattern and realizes the sub-nanometer measurement accuracy.
The mirror projection inspection system (e.g., see Japanese Patent Application No. 108864/1999) for detecting an electric characteristic failure on a circuit pattern is one of technologies for measuring circuit pattern states. The mirror projection inspection system radiates a planar electron beam onto a semiconductor wafer. An electron (hereafter referred to as a mirror electron) bounces and returns near the surface of a circuit pattern on the semiconductor wafer where a voltage is applied. The system uses a lens to image that mirror electron and generates a pickup image (hereafter referred to as a mirror image) for observation. An abnormal electric characteristic location on the circuit pattern is charged differently from a normal electric characteristic location. A mirror electron returning near the abnormal electric characteristic location is imaged with an orbital different from the one for a mirror electron returning near a normal electric characteristic location. Therefore, observing the mirror image makes it possible to detect an abnormal electric characteristic location.
The AFM (Atomic Force Microscopy) for measuring a heightwise shape of a circuit pattern is one of technologies for measuring circuit pattern states. The AFM scans a specimen surface using a fine needle with a tip curvature of sub-micrometers. The AFM images a heightwise travel distance of the needle in synchronization with the scanning to measure the specimen's heightwise shape.
The AFM can detect heightwise variations of a specimen. However, the AFM's measurement accuracy largely depends on the needle's scanning speed. Increasing the scanning speed degrades the accuracy. It takes a long time to accurately detect heightwise variations of a specimen over a wide range.